1. Field of the Invention
The present invention relates to a voltage generator, and more particularly, to a DC voltage generator which has a fast response time.
2. Description of the Prior Art
In a dynamic random access memory (DRAM) which adopts a double data rate DDR4 standard, an internal DC voltage generator is used by a DQ receiver to determine a received signal to be a logic value “0” or “1”. Please refer to FIG. 1, which is a diagram illustrating a conventional DC voltage generator 100. As shown in FIG. 1, the conventional DC voltage generator 100 includes a controllable voltage divider 110, a regulator 120 and capacitors C1 and C2, where the controllable voltage divider 110 includes a variable resistor R1 and a resistor R2, and the regulator 120 includes a power amplifier 122, a transistor M1 and two resistors R3 and R4.
In the operations of the conventional DC voltage generator 100, a voltage level of a regulated voltage VREFD of the conventional DC voltage generator 100 is controlled by a control signal MRS. When the control signal MRS instructs the conventional DC voltage generator 100 to increase/decrease the output voltage VREFD, the output voltage VREFD may require a long period of time to achieve the required voltage level; in other words, the response time is slow. To improve the response time, one solution reduces the capacitance of the capacitors C1 and C2, but the power supply rejection ratio (PSRR) and stability of the conventional DC voltage generator 100 will be worsened.